I’m now in the editing stage of my upcoming book Zombies of Byzantium. Although the book has been written and rewritten several times, and now has gone under the gaze of a senior editor and a copy editor, I’m still battling a very old and elusive enemy: physical continuity.

For example, in Chapter 9 of Zombies of Byzantium, the main character, Stephen Diabetenos, battles zombies with a sword in each hand. At some point during the desperate battle he drops one sword, or at least I thought he did. But later on in the chapter I refer to him as dropping one of his swords, implying he still has the other. The copy editor caught this. “He already dropped one sword outside the church,” the copy-editor wrote in the margin. “He originally picked up only two.” I went back and checked–yes, a couple of pages earlier Stephen drops one of his swords when a zombie springs up unexpectedly, startling him.

I groaned when I saw this because I remember originally writing the scene more than a year ago and agonizing over continuity like this. The scene is a huge battle involving numerous characters, armed with various weapons. I kept notes of who was where, who had what weapon, who was doing what to whom at any given time, etc., but evidently I still got it wrong. If you’re writing scenes that involve a lot of action like this, and you put in a lot of detail, it becomes difficult to keep track of everything. Somewhere you’re going to slip up.

Film directors employ crew members whose sole job is to watch for errors like this. If the hero has been wounded in the left arm in one scene, it had better be his left arm in a sling in the next scene–not his right. If a woman is shown putting on coral lipstick before dinner, she’d better be seen wearing the same color lipstick in the dinner scene. If you’re writing it, however, you have only yourself to rely on. Yes, a good copy editor or beta reader may catch errors like these, but an author shouldn’t rely on them to do it. He or she should take care of these things on the front end.

In order to keep track of things like this, I sometimes block my scenes out on paper exactly the way a film or play director would for a physical performance. Or at least I keep a list of relevant facts. Make sure you know where your characters are at any given time, what they’ve got in their hands, what they’re wearing or anything else about them that’s relevant enough to mention in the narrative, especially if it’s likely to change. When the scene is done, go back and read it again–several times, in fact–to make sure you’ve got everything straight.

Just as a glaring continuity error in a movie telegraphs a sloppy director, continuity gaffes in writing will raise the hackles of your readers. Sometimes a little thing like “But he already dropped one sword!” will bother them more than a serious matter like, “There’s no motivation for the villain’s actions in that scene!” You’d be surprised what readers are willing to forgive and what they aren’t. It’s better just not to go there at all.